Optofluidic Devices For Biological And Energy Applications

Abstract

Optical energy is one of the most ubiquitous form of energy available and as such, has been the source of abundant research into understanding and developing applications using it. The versatility and sensitivity of optical forces have allowed it to be widely applied in both micro/nano scales and macro scales. Herein, I discuss the development of two further devices to take advantage of the numerous benefits offered by optics. First, a soft gel based optical waveguide is fabricated and experimentally tested. The gel waveguide, fabricated from agarose hydrogel, extends the capability of optical manipulation from silicon and other hard substances to soft materials capable of incorporating biology within the substrate itself. We demonstrate this by incorporating live cells within the core of the optical waveguide where they can be probed by the strong optical field. A microfluidic channel is also integrated thus developing a complete optofluidic configuration for biological studies. In the second part of this work, the development of a stacked waveguide photobioreactor for algae-based biofuel production is described. The benefits of the thin light paths and uniform light distribution achieved due to the stacked waveguide architecture are demonstrated by investigating biomass growth and ethylene production from genetically engineered cyanobacteria. Growth rates are found to be eightfold greater than a control reactor, sustained ethylene production is achieved for 45 days, and ethylene production rates two times greater than that of a conventionally run photobioreactor are demonstrated. These capabilities are further improved by optimizing the wavelength and the intensity of the incident light. The thin light paths present in the photobioreactor allow for large carrying capacities with optical densities of over 20 capable of being sustained in the photobioreactor. Optimization of all these parameters led to a further two fold improvement in ethylene production rates leading to an overall fourfold increase over a conventionally run photobioreactor. Besides the experimental verification, theoretical models for light and thermal distribution within the stacked photobioreactors were also created. These results thus provided justification for the stacked waveguide design and exploration for development of a larger scale model.